The object of the invention is to create a method and a device for detecting the reason for combustion misfires or that the said method and device for accurately detecting the reason for combustion misfires is accurate.
The object of the invention is achieved by the features of the independent patent claims. Advantageous further embodiments of the invention are characterized in the sub-claims.
The invention in accordance with a first aspect is characterized by a method and a corresponding device for detecting combustion misfires in a combustion chamber of a cylinder of an internal combustion engine with a plurality of cylinders that have been allocated in at least two groups to one exhaust gas tract each. In each exhaust gas tract, an exhaust gas catalytic converter and an exhaust gas probe are fitted upstream of the exhaust gas catalytic converter. Combustion misfires are detected in one of the cylinders in accordance with at least one operating variable of the internal combustion engine and allocated to one of the groups of the cylinders. A cause of the error of combustion misfires is determined and lies in an injection system of the internal combustion engine or in an ignition system of the internal combustion engine depending on a first standard difference of a lambda regulator, which has been allocated to the group of cylinders, which has been allocated to the combustion misfires and, moreover, depending on a second standard difference of an additional lambda regulator, which has been allocated to one group of the cylinders, which has not been allocated to the combustion misfires.
According to a first aspect, the invention applies the knowledge that when the cause of the error is determined, it is possible that influences that are not caused by combustion misfires and which could possibly lead to an incorrect conclusion on the cause of the error could be reduced in this way, because they have an effect on both with regard to the group of cylinders, which has been allocated to the combustion misfires and on that group of cylinders, which has not been allocated to the combustion misfires. Above all, it is for example possible that in the event of an estimated value for a mass air flow in the cylinders of the internal combustion engine or additional load variables, which have been determined by means of a dynamic physical model of an exhaust gas tract of the internal combustion engine, the influence of a modeling fraught with errors is reduced. Over and above that, with regard to the first aspect in the case of low combustion misfiring rates, it is possible to allocate the cause of the error in an accurate manner.
The invention in accordance with a second aspect is characterized by a method and a corresponding device, which is distinguished from that in accordance with the first aspect in that the cause of the error of the combustion misfire is determined depending on a first characteristic value, which is determined depending on the controller output of the lambda regulation, which has been allocated to the group of cylinders, which has been allocated to the combustion misfires and, moreover, which is determined depending on a second characteristic value which is determined depending on the controller output of the lambda regulation, which has been allocated to one group of the cylinders, which has not been allocated to the combustion misfires.
In accordance with the second aspect of the invention, the invention applies the knowledge that the first characteristic value is influenced by the combustion misfires whereas the second characteristic value is not influenced by the combustion misfires. Due to the effect of the interferences on both characteristic values, it is possible that because of the corresponding determination of the cause of the error, depending on the first and the second characteristic value, the influence of the interferences is reduced or even eliminated and because of this it is in particular possible to determine the cause of the error in a reliable manner. Above all, it is also for example possible here, in the event of an estimated value for a mass air flow in the cylinders of the internal combustion engine or another load variable, which is determined by means of a dynamic physical model of an exhaust gas tract, an influence of a modeling fraught with errors is reduced. Over and above that, in the event of a high combustion misfiring rate, it is possible to allocate the cause of the error in an accurate manner.
A combination of the first and the second aspects of the invention has the advantage that both in the case of low combustion misfiring rates and in the case of high combustion misfiring rates, the cause of the error can easily be allocated in an accurate manner.
In accordance with an advantageous embodiment of the invention, the first or the second characteristic value is determined in such a way that it is representative of an integral part of the output controller of the specific lambda regulation. In this context, the knowledge is applied that the integral part is representative of a stationary regulator intervention of the specific lambda regulation, which on the other hand, is characteristic of the occurrence of combustion misfires in particular with a high combustion misfiring rate.
In this context, it is advantageous if the first or the second characteristic value is determined depending on taking a sliding mean for the controller output of the specific lambda regulation. In this way, it is in particular possible to determine the stationary regulator intervention in an easy manner.
In accordance with an additional advantageous embodiment of the invention, the cause of the error is determined depending on a first trim characteristic value, which is determined depending on a controller output of a trim regulator, which has been allocated to the group of cylinders, which has been allocated to the combustion misfires and, moreover, which is determined depending on a second trim characteristic value, which is determined depending on the controller output of a trim regulator, which has been allocated to the group of cylinders, which has not been allocated to the combustion misfires. Therefore, it is in particular possible in this way to allocate the cause of the error in a correct manner, in particular, in the case of average and high combustion misfiring rates. A trim regulator is characterized in that its controller output is determined depending on a measuring signal of an exhaust gas probe, which is fitted downstream of the specific exhaust gas catalytic converter and in this way it is in particular possible to compensate for a behavior of the specific exhaust gas probe that is fitted upstream of the exhaust gas catalytic converter changing over the operating time of the internal combustion engine.
In accordance with an additional advantageous embodiment of the invention, the cause of the error is determined depending on the desired value for the air-to-fuel ratio, which has been allocated to the group of cylinders, which has been allocated to the combustion misfires. In this context, the desired value preferably relates to that value at which the gas flow times and the probe dynamics of the exhaust gas probe upstream of the exhaust gas catalytic converter and, if required, a behavior of the exhaust gas catalytic converter are taken into account. Therefore, it is in particular also possible in this way to allocate the cause of the error to a full load operation of the internal combustion engine or in this context to an enrichment of the air-to-fuel mixture supplied to the internal combustion engine in order to protect the exhaust gas catalytic converter in a very accurate manner.
Over and above that, it is also possible to reduce or eliminate the effect of interferences by means of a superposed forced excitation in the case of the lambda regulation, which could otherwise act as interferences with regard to determining the cause of the error.
In accordance with an additional advantageous embodiment of the invention, the cause of the error is determined depending on a cylinder-specific uneven running value of said internal combustion engine, which has been allocated to the cylinder in which the combustion misfires were detected, and allocated to the other cylinders depending on additional cylinder-specific uneven running values of said internal combustion engine. In this way, it is in particular possible in the case of sporadic combustion misfires whose frequency increase with a decreasing quantity of fuel, to allocate very accurately the cause of the error, if it is in the injection system. In this context, the knowledge is applied that in the case of this cause of the error, which is also called low flow, also in the case of points in time or operating conditions, in which there are no combustion misfires or hardly any combustion misfires occur, the uneven running of the internal combustion engine has clearly changed compared to additional cylinder-specific uneven running values of said internal combustion engine, which have been allocated to the other cylinders even when its absolute value has not yet reached the value that is characteristic of combustion misfires.
In accordance with an additional advantageous embodiment of the invention, the cause of the error is determined depending on a cylinder-specific duration of the spark of an allocated spark plug, which has been allocated to the cylinder, in which the combustion misfires were detected, and depending on additional cylinder-specific durations of the spark of other spark plugs, which have been allocated to other cylinders. In this way, it is in particular possible in the case of operating points of the internal combustion engine with a low cutoff that the cause of the error can be clearly allocated in an accurate manner. Above all, it is possible in said way that the cause of the error in the ignition system can be determined in an accurate manner. This is based on the knowledge that in particular in the case of the operating points of a low cutoff, exhaust gas packages that have been allocated to the individual cylinders on reaching the upstream exhaust gas probe have very often to a large extent already been mixed with the exhaust gas packages of other cylinders. Therefore, this results in the fact that a cylinder-individual influence on actually occurred combustion misfires in one of the cylinders, less characteristically with a view to the allocation to the specific cylinder influences the first standard difference of the lambda regulation, which has been allocated to the group of cylinders, which has been allocated to the combustion misfires, and influences less characteristically the controller output of the lambda regulation, which has been allocated to the group of cylinders, which has been allocated to the combustion misfires.
In accordance with an additional advantageous embodiment of the invention, the cause of the error is determined by evaluating a plurality of detected combustion misfires, which has been allocated to the group of cylinders, which has been allocated to the combustion misfires. In this way, it is possible to remove statistical fluctuations, in particular a vibration, by means of filtering and indeed, with a high probability and in this way the assurance of a correct allocation of the cause of the error is increased.
In this context, it is in particular advantageous if the number of the majority of detected combustion misfires depends on a rotational speed and/or a load variable. In this way, it is then in particular possible in the different operating areas of the internal combustion engine to carry out the allocation of the cause of the error in an accurate manner.
In accordance with an additional advantageous embodiment of the invention, the cause of the error is determined by evaluating the majority of detected combustion misfires, which were detected during a predetermined point in time. In this way, it is also in particular possible to carry out an accurate allocation in an easy manner.
In accordance with an additional advantageous embodiment of the invention, the predetermined point in time depends on the rotational speed and/or a load variable. In this way, it is also in particular possible to carry out in the different operating points an accurate allocation of the cause of the error.
In accordance with an additional advantageous embodiment of the invention, the cause of the error is determined depending on a combustion misfiring rate of a specific cylinder, which has been allocated to the group of cylinders, to which the combustion misfire has been allocated, and/or a probe ageing of the exhaust gas probe which has been allocated to the group of cylinders to which the combustion misfires have been allocated. In this way, it is in particular possible to guarantee a reliable allocation of the cause of the error and this in particular over a long operating time of the internal combustion engine.
Elements with the same design and function are characterized in all the figures with the same reference symbols.